Invasion of the Body Snatchas! is a clone of the arcade shooter Defender where you fly over the surface of a planet protecting women from the marauding aliens. Landers, Mutants, Bombers, Pods, Swarmers and more aliens threaten the world and the job at hand is to decimate the alien invasion force while protecting the women.
Landers will swoop down and attempt to grab your women and if they succeed in bringing them to the top of the screen, they will turn into a crazed alien that will hunt the player craft down.
Your craft has a laser and a limited amount of smart bombs that kill every alien on screen and it can fly in both horizontal directions. At the top there is a long range scanner that can be used to anticipate where on the screen the aliens appear.
If you hit any alien or an alien projectile, then you lose one of three lives, once all lives are spent, it's game over.